The present invention relates generally to a rotary drum as used in the granular product drying field, and having a major application for the treatment of heated and moist granular products such as mold sands, grains, and fertilizers as to achieve the reclaiming, cooling, and blending of the mold granular product and in particular, to a dust collection hood and discharge chute configured to convey multiple air streams through the rotary drum for the cooling of the granular product.
There are a variety of prior patents that have been obtained upon various styles of rotary drums for use in the metal casting industry. For example, one of the early embodiments is that which is shown in U.S. Pat. No. 3,998,262 to Charles J. Didion, showing a casting shakeout unit and method of operation. Essentially, such a drum is arranged upon its structural support and rotated by means of a drive unit, so that when castings clogged with mold sand as obtained directly from the site of their casting, are then passed through the rotary drum, the mold sand is effectively separated and removed from the prepared castings, to achieve the required separation without necessitating the employment of any manual labor to attain such results.
The usage of shrouds or hoods around the discharge end of the rotary drum has been employed in the prior art, as can be seen in U.S. Pat. No. 4,050,635 to Mueller, et al., wherein the shown housing incorporated an outlet chute, at is lower end, for attaining the discharge of the castings, or its sand, therefrom, during operations of the shown device. In addition, such hoods have been used for collection and removal of sand particles, to facilitate the collection of the sand in preparation for its re-usage.
Similarly, the usage of a ventilating hood on a rotary drum, having various ventilating ports designed therein so as to accommodate the flow of air around and through the discharge end of the rotary drum, for the removal of heat from sand and containment of fines and dust, while likewise diverting the separated mold sand for passage to a discharge opening, as arranged at the bottom of the ventilating hood is shown in U.S. Pat. No. 4,981,581 to Charles J. Didion.
However, it has been found that the removal of heat from hot granular products by exposure to an airflow only at the discharge end is insufficient to reduce the temperature of the granular products to near ambient temperatures. Accordingly, there is a need for a reclaiming rotary drum configuration which is capable of removing heat and moisture from granular products from the point of intake through the discharge end, to increase the heat removal, and to reduce the granular product temperature to near ambient conditions at the discharge end.